Mercruiser 5.0 how much HP?

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jdskidawg

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so i have been thinking about doing some upgrades to my 5.0. its a 99 with the vortech heads and is stalk for now with a 2bbl carb at 220 hp. Everybody says its not wroth the money, and that i wont gain much and that typically its about 1000$ to go 1 mph faster! the upgrades im thinking is 4bbl carp and some revolution manifolds! that would cost me around 1800 bucks if i do it myself. my question is how much Hp would i need to spinn a larger prop at the same wot or if its even possible i am running a 19p highfive and would like to run a 21p that would increase my speed and performance. no?

any comments or feedback is appreciated

thanks

JC
 
45Auto

45Auto

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Re: Mercruiser 5.0 how much HP?

You might find this thread interesting where Craze1cars swapped his 1999 5.0L two barrel for a four barrel carb and reported the results:

http://forums.iboats.com/showthread.php?t=396275&highlight=volvo+manifold

A rough rule of thumb is that you have to add about 10 HP to gain 1 MPH on your boat. Carb, exhaust, etc, (have to add a manifold into that if it's a Merc) might gain you 20-30 HP which would translate into 2-3 MPH more speed. You'll have to decide how much that's worth to you.
 
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John_S

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Re: Mercruiser 5.0 how much HP?

The revolution manifolds will probably be $1800 and 0 mph faster. You are not exhaust restricted on a 5L w/through prop exhaust and spinning 5K or less rpms.

Unlike a recent thread on Volvo/vortec/5.0L, where there was zero diff between 2brl and 4brl, you should see some on a Merc. I believe the 2 brl is less than 500cfm and the Merc intake is more restictive than the volvo. The 4brl intake/carb/flame arrester will run about $1000, and maybe get 1-2mph.
 
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jdskidawg

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Re: Mercruiser 5.0 how much HP?

imported_John_S said:
The revolution manifolds will probably be $1800 and 0 mph faster.

Unlike a recent thread on Volvo/vortec/5.0L, where there was zero diff between 2brl and 4brl, you should see some on a Merc. I believe the 2 brl is less than 500cfm. The 4brl intake/carb/flame arrester will run about $1000, and maybe get 1-2mph.
Click to expand...

you can get the black Powdercoated for around 900 an ya about 1000 for the 4bbl upgrade will that be enough hp to spin a 21p prop ya think? if i can spin a 21p prop at the same WOT i will gain almost 5 mph using a according to a prop calculator
 
Bondo

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Re: Mercruiser 5.0 how much HP?

Ayuh,.... For that kinda money, Sell the 5.0l,+ drop in a 350.... That's an Up-Grade....
 
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jdskidawg

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Re: Mercruiser 5.0 how much HP?

Bond-o said:
Ayuh,.... For that kinda money, Sell the 5.0l,+ drop in a 350.... That's an Up-Grade....
Click to expand...

thought about that but my boat is only rated for max 260 hp so i dont want to go much over that!
 
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John_S

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Re: Mercruiser 5.0 how much HP?

jdskidawg said:
you can get the black Powdercoated for around 900 an ya about 1000 for the 4bbl upgrade will that be enough hp to spin a 21p prop ya think? if i can spin a 21p prop at the same WOT i will gain almost 5 mph using a according to a prop calculator
Click to expand...

Ok, well $900 and 0mph.

You may get 20hp out of it, but not 50. If you can spin a 21" will depend on the test runs with your current 19".
 
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jdskidawg

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Re: Mercruiser 5.0 how much HP?

imported_John_S said:
Ok, well $900 and 0mph.

You may get 20hp out of it, but not 50. If you can spin a 21" will depend on the test runs with your current 19".
Click to expand...

im not looking for mph im looking for hp and you say that i will only get 20 hp increas going with a 4bbl carb and new manifolds? or am i not going to get any gains from the manifolds at all?

and spinning the 21p prop would depend on the hp im running right? or am i wrong in thinking that?

220hp spining my 19 maybe 260hp will spin a 21 ?
 
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robjen1019

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Re: Mercruiser 5.0 how much HP?

don't know why anyone would go to the work and expense of upgrading a 5.0, when any old stock 5.7 will easily out power it. Upgrading the top end might get you 1 to 3 mph, but won't do much at all for low end or torque. Just buy the long block and switch everything over. Hell, you really want to do it right, put a 383 in there and be done with it.
 
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jdskidawg

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Re: Mercruiser 5.0 how much HP?

robjen1019 said:
don't know why anyone would go to the work and expense of upgrading a 5.0, when any old stock 5.7 will easily out power it. Upgrading the top end might get you 1 to 3 mph, but won't do much at all for low end or torque. Just buy the long block and switch everything over. Hell, you really want to do it right, put a 383 in there and be done with it.
Click to expand...

AGAIN! the boat is only rated for max 260 hp so dropping in a 383 would not be the brightest thing to do! swapping out the whole motor for a 5.7 seems like a waste when i can just do some slight mods and probably get it to the max hp rating! was just coming up with some ideas and had some questions! looking for input!

thanks
 
wire2

wire2

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Re: Mercruiser 5.0 how much HP?

"There's no replacement for displacement"
 
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John_S

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Re: Mercruiser 5.0 how much HP?

jdskidawg said:
im not looking for mph im looking for hp and you say that i will only get 20 hp increas going with a 4bbl carb and new manifolds? or am i not going to get any gains from the manifolds at all?

and spinning the 21p prop would depend on the hp im running right? or am i wrong in thinking that?

220hp spining my 19 maybe 260hp will spin a 21 ?
Click to expand...

No, you are looking to go to a 21" prop, and to reach wot rpms with that will take hp. I just used your 5mph estimate with the "general" rule to get 50hp. From experience, it takes more than 10hp to gain 1 mph. Allot depends on your hull. If you have a light and fast hull, maybe the "rule" is good.

Are you at the top of your wot range with full load today?

My estimate is based on a new intake manifold and a 4brl carb.

I am saying the exhaust manifolds are a waste of money. Ask anyone with a captains call on a 5.0 or 5.7L. Might gain a little on a 383. Even with adding a 4brl, it is basicly just a stock engine with stock cam.


Your boat rating is probably just based on the largest option available on that particular hull. Not the most it could handle. Running a 5.7L is not going to turn your transom to mush, but those insurance adjusters are always looking for an out..
 
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John_S

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Re: Mercruiser 5.0 how much HP?

jdskidawg said:
AGAIN! the boat is only rated for max 260 hp so dropping in a 383 would not be the brightest thing to do! swapping out the whole motor for a 5.7 seems like a waste when i can just do some slight mods and probably get it to the max hp rating! was just coming up with some ideas and had some questions! looking for input!

thanks
Click to expand...

To get 260hp at the prob, you will need a cam change and the vortec heads will need to be mod'ed to handle the lift. New valve springs, too. If this is an alpha drive, you need to keep the idle rpms down, can't go too drastic with cam.
 
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